The potential threat of biological and chemical agent warfare is an ever-increasing national security concern. Of the known biological and chemical warfare agents it has been suggested that those capable of being deployed as aerosols are of greatest concern. Four of the five Centers for Diseases Control and Prevention Category A bioterrorism agents are capable of being transmitted as bio-aerosols, including Bacillus anthracis, more commonly known as “anthrax.” Unfortunately, the detection of such biological attacks is inherently difficult due to the small sample sizes. For example, a lethal dose of Bacillus anthracis spores weighs only 4 ng. In addition, these small samples can be widely dispersed within the air and may be found mixed with many other aerosol particles present in concentrations thousands of times larger than the bio-aerosol of interest. These demanding sampling conditions and other detection issues such as the unreliability of real time particle source analysis, let alone identification, have been problematic for the rapid screening of packages, letters, baggage, passengers, and shipping containers for biological and/or chemical agents.
While various particle detection methods have been and are currently employed, such as PCR or immuno-assay techniques, they are incapable of real-time analysis and onsite identification of particle source, including threat agents. Moreover, many “online” and “real time” particle detection and analysis systems simply provide sorting of spectral data into similar groups (e.g. via fuzzy logic algorithms) for subsequent visual identification by an expert user. Thus, current methods and systems of “real-time” particle detection, analysis and identification may present too substantial a disruption of commerce to be used as a pragmatic alternative. There is therefore a need for a truly real time particle detection system providing rapid or virtually instantaneous identification of a single aerosol particle from among known particle types or sources, and which goes beyond a simple determination of a particle's chemical composition from mass spectra. Moreover, the ability to rapidly detect and screen bio and chemical aerosols within a complex mixture of background particles would aid in the detection and interdiction of bioterrorist attack.